Survey on Pulsed Electron Beam Deposition Work in Technique and Medicine, страница 2

Procedure

Foil type

O2-permeation

Remarks

12µm polyester uncoated

108

Uncoated

Physical vapor

12µm polyester, 30 nm SiO2

<10

Only as compound, Coating is instable

Physical vapor

12µm polyester, 20 nm Al coated

<0.1

Lowest permeation, but food is not visible

PED CS

12µm Polyester, glass coated

3

Layer stable, transparent

MEDICAL COATING WORK

By controlling the repetition rate even temperature sensitive hydrocarbons can be coated (see Chap. before). Targets used in PED can be dielectric materials. This opens the way to coat all kinds of medical implants with bio-active glasses [5] (Figure 3). Normally very brittle, bio-active glasses in form of thin coatings, i.e. 10 µm thick are flexible and give implants the desired bio-active surface. The perspective is not only hard tissue bonding (bone implants) but also soft tissue anchoring since the phase diagram of bio-active glass shows a small area with this behavior (see Figure 4). To stay within the acceptable stoichiometry deviations from the coating, procedure must be controlled accurately. Fortunately ablation in PED takes place in form of small molten droplets with a characteristic diameter of 40 nm. Inside the droplets the stoichiometry does not change. This gives hope to reproduce the same tissue anchoring potential for the film as for the bulk material shown in the phase diagram of bio-active glasses. The thickness of the coating in Figure 3 is 14 µm. The coating has to be sufficiently thick because a solution attack occurs in body liquids, accompanied by a hydroxyapatite (HA) crystal growth. Phosphorous groups at the surface of HA are responsible for the tissue anchoring. The adhesion of the coating is measured to 200 N/cm². This result is a consequence of a pretreatment of the substrate by means of Argon sputtering.

FIGURE 3. Test substrates from TiAlV used in in-vitro and in-vivo experiments. Substrates (right) are coated with 14 5m thick bio-active glass; the left one is uncoated.

FIGURE 4. Phase diagram of bio-active glass

Other Applications

Actual efforts are the development of High-Tc-Superconductor cables, production of Nanotubes, organic LEDs, spin-coupling by means of ferromagnetic films and the coating of metallic or plastic medical implants with bioactive glasses (see ref. [4]). Other applications are the coating of plastics with 100 nm barrier layers to reduce the permeation of gases. Related tasks are the coating of ink cartridges made of plastic with a glass layer to prevent drying out. Another field of application is the ablation of PE, Polystyrene, PTFE etc. for coating surfaces. Besides optical effects of aesthetic value, PTFE coatings have a low molecular weight, are soft and can be used as extra thin sealants (thickness 40-100 µm) in aggressive environments in chemical industry.

Outlook

PED opens the possibility to coat nearly all kinds of substrates with functional materials. This might have good perspectives in the wide field of technological applications. Actually the procedure is already accepted and used in high-tech industries.

Acknowledgments

The authors would like to thank the European Union for the support of this project in the frame of the 6^th framework of Competitive and Sustainable Growth.

References

1. Müller G., Konijnenberg M., Krafft G., Schultheiss C. Deposition by Means of Pulsed Electron Beam Ablation // Science, technology of thin film, edited by World Sci. Pub. Co. PTE. LTD, 1995.

2. Foltyn S. R. et al. Superconductivity Program for Electric Systems, Annual Peer Review, Aug. 1–3, 2001, Washungton D. C.

3. Schultheiss C. et al. Progress on Channel Spark Development, Beams 2002, 14^th Int. Conf. on High Power Particle Beams, Albuquweque, New Mexico, 23–28 June 2002, 321.

4. See: http://www. codeangel. com/neocera/html/display. asp?recno=70, http://www. organic-spintronics. com

5. Wilson June, Nolletti D. Bonding of Soft Tissue to Bioglass .. Handbook of Bioactive Ceramics, edited by T. Yamamuro, L. L. Hench, J. Wilson. CRE Press. Boca Raton, FL (1990), http://www. bg. ic. ac. uk/Lctures/Hensch/BioGlass/call3. htm